Aplication of Sorting Grid on Crayfish, Pontastacus leptodactylus, Fyke Net
Project no. 21737 · Status: Kapanmış · 2020
Summary
Aplication of Sorting Grid on Crayfish, Pontastacus leptodactylus, Fyke Net; In this study was carried out on grid systems to both improve size selectivity and facilitate harvesting in commercial crayfish (Pontastacus leptodactylus) fishing. the natural crayfish In addition to commercial fyke (control group) net used as commercially nine new grid system which shown different opening directory (I; fully opened in two parts from the axis towards the edge, II; half opened in one piece from the edge to the axis direction, III; half opened in one piece from the axis towards the edge) and 3 different bar spacings (18 (Izg18), 20 (Izg20) and 22 (Izg22) mm), a total of 10 different systems were tested. Study carried out in the two steps both selectivity and ergonomic properties of the experimental. Covered codend method used for determination of the selectivity. Grids were implemented on traditional fyke nets and surround with cover codend. Cover 1 (for escaping from the grid) and Cover 2 (for escaping from the meshes of fyke net) were designed. Ten experimental fyke net rigged for each group. Developed grids were implemented on end of the traditional codend and produced for each groups ten units. A total of 1697 crayfish were caught with total length range between 35.95- 162.10 mm. Retained crayfish consist of 774 females (45.6%) and 923 males (54.4%) individuals. L50 values were estimated as 8.42 cm (8.24-8.50) for Izg18 (Cover1), 8.97 cm (8.82-9.13) Izg18 (Cover2), 8.98 cm (8.84-9.13) and Izg18 (Cover 1+Cover2), 9.11cm (8.48-9.53). For Izg20 (Cover1), 9.29 cm (9.22-9.44) Izg20 (Cover2), 9.29 cm (9.14-9.40) and Izg20 (Cover1+Cover2), 9.00 cm (8.66-9.33). for Izg22 (Cover1) 9.79 cm (9.64-9.94), Izg22 (Cover2), 9.79 cm (9.63-9.93) and Izg22 (Cover1+Cover2). Finally, 8.15 cm (7.91-8.41) for traditional codend. Mean harvest time determined as 31.34, 31.74, 30.81 and 31.28 s for Izg1, Izg2, Izg3 and traditional codend. There were no significant differences between mean harvest time(p>0.05). As result, using of the grid system was improved of length selectivity of the fyke net in addition to grid with 22 mm bar length was evaluated as best selective gear when consideration of MLS. Mean harvest time of all developed grid system were very close the traditional one, but the best result was gained from type three.